Electric furnace and method of carbonizing metallic charges therein



June 26, 1928.

' 1,674,982 w. E. MOORE ELECTRIC FURNACE AND METHOD OF GARBONIZING METALLIC CHARGES THEREIN Filed May 11. 1922 Patented June 26, 1928.

UNITED STATES- wnmurn. moon, on PITTSBURGH, PENNSYLVANIA, assronon.

PATENT orrlca.

RESEARCH CORPORATION, A CORPORATION OF DELAWARE.

Application filed May 11,

This invention relates to metallurgical electric furnaces of the arc type, and more particularly toan improved method of carbon'izing metallic charges in such furnaces.

It has heretofore been the common practice to construct the hearth or bottom of arc type metallurgical furnaces of refractory material, such as magnesite, dolomite or ganister, which becomes electrically conducting at high temperatures. It has also been proposed to construct furnace bottoms of this kind of a layer of refractory material which is of progressively increasing conductivity from the top downward.

Such abottom, however, does not give the best results for certain classes of work, and I now pro se to provide a furnace bottom consisting of a layer of substantially uniform hi h conductivity throughout. I have also ound that when treating such metals as iron or steel for the purpose of carbonizing them, it is desirable to form the furnace bottom or hearth of carbon or car-- bonaceous material capable of giving up as carbon to the charge.

The present invention also seeks to facilitate the carbonizing of a metallic charge by agitating the same while in contact with such a' carbonaceous bottom or hearth, and

I have discovered that the carbonizing action can beexpedited b mixing carbonaceous material with the c arge and then agitating the charge while such material floats upon the surface thereof.

In order that the invention may be more readily understood, reference is had to the accompan in draw forming a partof .thisspec' cation and ustrating in vertical section a three phase furnace constructed in 40 accordance with the invention and showing my improved means for agitating the charge.

Referring to the drawing indetail, .the furnace is designated in its entirety by the reference numeral 1-, and is shown as supported upon rockers 2 resting upon rollers 3 mounted on a concrete foundation 4. By

virtue of this method of mounting, the fur nace may be tilted so that the molten charge can be poured from the spout 5.

My improved furnace bottom consists of an outer shell 6 formed'of metal plates, and a supporting layer 8 of refractory material such as basic or neutral brick, a lining 7 1922. serial- No. 560,126.

of suitable mortar being preferably interposed between the shell 6 and refractory layer 8.

The/topmost or active layer 9, constituting the bottom or hearth of the furnace which is in direct contact with the charge, rests upon the layer 8, and consists of carbonaceous'material such as carbon, or graphite, .or a carbonaceous compositon such as a mixture of graphite with ferro-alloys or other,

metals. This layer 9 constitutin the bottom 'or hearth proper is of su stantially uniform high conductivity throughout, and is electrically connected to the metallic shell 6 by means ofa plurality of metal stri or fins 10 secured at one end to the shell 6, and having their other ends embedded in the layer 9 of carbonaceous material, such fins or strips extending .through the refractory supporting layer 8.

The furnace is illustrated'as hav' electrodes (1, I) and 0, extending t rough the roof as usual, and connected to -the ends of the secondary winding of a three phase transformer z, y, the secondary winding y being star .connected, and a conductor 2 extends from the neutral point of the star connected secondary to the metallic shell 6 of the-furnace, being secured thereto by means of a suitable chp 2'. Thus current not only passes from one electrode to the other, but may flow also from one or more carbonaceous material floats on topof the molten charge and mixes with the impuri ties to form a carbonizin slag. I have found then, that when the giarge is molten and in contact with theabove described carbonaceous bottom'or hearth at one side,

and in contact with the carbonizing slag on the other side, it can be very effectively car bonized by agitating the liquid mass.

In the drawing 11 designates the molten ems or liquid charge on which floats a slag 12 contaming lumps of solid carbonizing material 13.

There are several ways in which this liquid charge can be agitated. Thus, for

' example, fairly good results can be obtained by simply thrusting a pole of green Wood into the charge, the heat of the chargejimmediatey vaporizing the volatile constituents of the wood, thus' causing ebullition of the molten mass.

A more effective method, however, is to plunge into the molten charge the end of a pipe 14, such end being of course protected usual. door 19. The fluid employed maybe either a non-oxidizing or reducing gassuch as hydrogen, under pressure, or it may be in the nature of a hydrocarbon, either gaseous or liquid. In. either case the passage of the gases or vapors through the molten charge produces a violent bubbling or ebullition, thus agitating the mass and bringing all parts thereof into intimate contact with both the carbonaceous bottom and the carbonizing .slag.

Moreover, if a hydrocarbon or oil is em ployed the gases or vapors therefrom fill the spacein the furnace above the charge and themselves constitute carbonaceous or carbonizing material. Thus by using a fluid hydrocarbon for bubbling through the charge, it performs the doublefunction of agitating the molten mass and at the same time supplyin carbon which may be absorbed by the c arge.

Itwill therefore be understood that I contemplate carbonizing a metallic charge .in

improvedcarbonaceous bottom isfound to be highly'resistant to both acid and basic any one of the several ways mentioned orby employing all of the several methods at the same time. Thus I may omit thesolid carbonaceous material and produce the carbonizing simply by agitating the molten mass in contact with my improved carbonaceous hearth, or I may agitate the mass by means of a fluid hydrocarbon as described, or I may use an inert gas and employ solid carbonizg material in the form of a supernatant slag.

In addition to its carbonizing function, my

- what I claim is:

- 1. In the treatment of iron and other metals in an arc type electric furnace, the method of carbomzing the charge which consists in mixing therewith carbonaceous materiala'heating until molten, and then agitating the mixture of carbonaceous material and molten metal. 3

2. In the treatment of iron and other metals in a direct arctype electric furnace,

the method of carbonizing the charge which consists in melting it when in contactwith carbonaceous material and agitating themolten mass while still in contact with the carbonaceous material by bubbling therethrough a hydrogen containing'gas.

3. In the treatment of iron and other metals in an arc type'electric furnace, the method of carbonizing the charge which consists in melting it'when in contact with carbonaceous material and agitating the so molten mass While still in contact with-the carbonaceous material by-v bubbling therethrough a reducing gas.

4. In, the treatment of iron and other metals in .an arc type electric furnace, the method of carbonizing the molten'charge which consists in introducing into the fur- Y nace and plunging-beneath the surface of the molten charge a pipe having a heat insulated end, and forcing through such on pipe into the charge suitable quantities of fluid'hydrocarbons.

5. In the treatment of iron and steel in an arc type electric furnace, the method of carbonizing which consists in introducing lumps of carbonaceous -material' into the furnace with the cold charge, melting down the charge, and then agitatingthe molten charge while .the carbonaceous material floats on the surface thereof.

6. In the treatment of iron and steel in an arc type electric furnace, the method of carbonizing which consists in introducing into the. furnace carbonaceous material of such a nature that it floats on top of the molten charge, and then agitating such charge by causing to bubble therethrough a non-oxidizing flllld.

7. In the treatment of iron'and steel in an arc type electric furnace having a hearth or bottom of carbonaceous material, the method which consists in agitating the molten charge by plunging into the same from above apiece of pipe having a heat insulated end, and forcingtherethrough a non-oxidizing fluid which bubbles up through the charge while'the charge is in contact with the carbonaceous hearth.

8. In the treatment of iron and steel in an arc-type electric furnacehaving a hearth or bottom of carbonaceous material, the method which consists in introducing into the furnace carbonaceous material of such a nature that it floats on top of the molten charge, and then agitating such charge'while it is in contact with both the carbonizing hearth and the supernatant carbonaceous material. 2,,

' WILLIAM E. MOORE. 

